Media storage systems are well-known in the art and are commonly used to store data cartridges at known locations and to retrieve the desired data cartridges so that data may be written to and/or read from the data cartridges. Such media storage systems are also often referred to as autochangers or library storage systems.
A typical media storage system may include one or more different types of cartridge-receiving devices for holding the various data cartridges. For example, one type of cartridge-receiving device may comprise an individual cartridge storage location for holding a single data cartridge. Another type of cartridge-receiving device may comprise a cartridge storage rack or “magazine” for holding a plurality of data cartridges. In any event, such cartridge-receiving devices generally serve to provide storage locations for the data cartridges and may be arranged so that they form one or more vertical stacks, although other arrangements are also possible. A further type of cartridge-receiving device may comprise one or more cartridge read/write devices for reading data from and/or writing data to the data cartridges. Yet another type of cartridge-receiving device may comprise a mail slot for adding and/or removing data cartridges from the media storage system. These cartridge-receiving devices may be located at any convenient position in the media storage system.
The media storage system may also be provided with a cartridge-handling system for transporting the data cartridges between the various cartridge-receiving devices. For example, the cartridge-handling system may transport the data cartridges between the cartridge storage location or racks and the cartridge read/write device. Or for example, the cartridge-handling system may transport a data cartridge from the mail slot to a cartridge storage location or rack. A typical cartridge-handling system may include a cartridge-engaging assembly or “picker” for engaging the various data cartridges contained in the cartridge-receiving devices. In addition, the cartridge-handling system also typically includes a positioning device for moving the cartridge-engaging assembly among the various cartridge-receiving devices.
Media storage systems of the type described above are usually connected to a host computer system that may access or store data on the data cartridges. As an illustration, if the host computer system issues a request for data contained on a particular data cartridge, a control system actuates the positioning system to move the cartridge-engaging assembly along the cartridge storage locations until the cartridge-engaging assembly is positioned adjacent the desired data cartridge. The cartridge-engaging assembly may then remove the data cartridge from the cartridge storage location and carry it to the cartridge read/write device. Once properly positioned adjacent the cartridge read/write device, the cartridge-engaging assembly may insert the selected data cartridge into the cartridge read/write device so that the host computer may thereafter read data from, or write data to, the data cartridge. After the read/write operation is complete, the cartridge-engaging assembly may remove the data cartridge from the cartridge read/write device and return it to the appropriate cartridge storage location.
In use, it is often necessary to identify the data cartridges so that the desired data cartridge may be located and retrieved from the cartridge storage location, or for general inventory purposes. Typically, the data cartridge may be identified by machine-readable indicia such as a bar code label affixed to the data cartridge. A suitable illumination and detection system, such as a bar code reader, is usually mounted to the cartridge access device for reading the machine-readable indicia from the data cartridge. By way of example, when the cartridge access device is positioned adjacent the data cartridge, the bar code reader may be activated to illuminate and decode the bar code label on the data cartridge to identify the data cartridge. The bar code reader may also be activated to illuminate other machine-readable indicia (e.g., alignment markers) on the cartridge read/write device and/or on the cartridge storage locations for positioning the cartridge access device adjacent thereto.
In some instances, the illumination system may not evenly illuminate the machine-readable indicia. For example, light emitted by the illumination system may overlap in some areas, causing higher light intensities in the areas of overlapping light and lower light intensities in other areas. Such uneven illumination of the machine-readable indicia may cause the detector system to misread the machine-readable indicia, or in some instances, may even render the machine-readable indicia unreadable.